1. Field of the Invention
The present invention relates to a method for manufacturing a barrier layer of semiconductor device and, more particularly, to a method for manufacturing a barrier layer of semiconductor device to form a high purity TiN layer without performing Metal Organic Chemical Vapor deposition (MOCVD) process.
2. Description of the Prior Art
As is generally known, tungsten has been widely used to electrically connect upper and lower metal wire or metal wire and silicon substrate in semiconductor devices since tungsten has excellent thermal stability and step coverage. Before tungsten is deposited, Ti/TiN barrier layer is deposited ahead. The Ti layer of Ti/TiN barrier layer is used as a lower adhesive layer for the tungsten layer having poor adhesion with oxide layer and the TiN layer prevents reaction of the Ti layer and WF6.
On the other hand, As the semiconductor device has been highly integrated, the size of contact hole becomes decreased and the depth becomes increased, thereby increasing the aspect ratio. Therefore, the Ti/TiN layer deposition by conventional sputtering method has reached the limitation. Considering this limitation, Collimator sputtering method and Low Through Sputtering (LTS) method have been proposed as a solution. However, these methods also have several defects.
Recently, a new method has been proposed that the Ti layer is deposited by Ionized Metal Plasma (IMP) and the TiN layer is deposited by Metal Organic Chemical Vapor Deposition (MOCVD).
FIGS. 1 to 4 are drawings showing a conventional method for manufacturing a barrier layer of semiconductor device. Referring to FIG. 1, first, an interlayer insulating layer 12, such as oxide layer, is deposited to have a sufficient thickness on a semiconductor substrate 10, such as silicon substrate having a predetermined contact region. Thereafter, the part of the interlayer insulating layer 12 on the contact region of the semiconductor substrate 10 is completely removed in accordance with a photolithography to expose the contact region, thereby forming a contact hole 13.
Then, a Ti layer 14 is deposited to have a thickness of 50˜300 Å on the lower part and the side of contact hole 13 and on the surface of interlayer insulating layer 12 in accordance with IMP process.
Subsequently, a TiN layer 16 is deposited to have a thickness of 300˜900 Å on the Ti layer 14 in accordance with MOCVD process, wherein the TiN layer 16 has a very low density. And, Tetrakis Dimethylamidotitanium (TDMAT) gas is generally used as a precursor.
After the deposition of the TiN layer 16, as shown in FIG. 2, the TiN layer 16 is subjected to nitrogen (N2) plasma treatment, thereby transforming the TiN layer 16 having a low density into the TiN layer 26 having a high density, as shown in FIG. 3. Therefore, a barrier layer is completed, comprising the Ti layer 14 and the TiN layer 26.
After the barrier layer is formed, a tungsten layer is filled only in the contact hole in accordance with a conventional process. Then, a metal layer, such as aluminum layer, is formed on the barrier layer outside of the tungsten layer and the contact hole and a photolithography process is performed to complete a metal wiring pattern.
However, the conventional method has several problems that the TiN layer 26, formed by MOCVD process, has inferior properties and aging effect that properties are changed as time passes. And, the MOCVD device is very expensive and difficult to maintain. Moreover, the TDMAT gas is highly toxic and inflammable, thereby increasing possibility of accident and having a bad effect on the environment. And, as the TiN layer 26 is damaged by impurities such as residual gas, the properties of the TiN layer 26 are deteriorated. The TiN layer 26 may also be damaged during the plasma treatment.
Moreover, as shown in FIG. 3, it is difficult to perform plasma treatment on the sidewall of contact hole 13, thereby impurities, such as residual carbon (C), tend to remain on the TiN layer 26 located on the sidewall of contact hole 13.